This invention relates in general to the preparation of products and, more particularly, to a method and apparatus for freezing products such as foods.
Many types of food products are frozen and then packaged as part of the process for preparing the food for distribution. This type of preparation is desirable because it extends the shelf life and freshness of the food beyond that which can normally be obtained if the food is maintained at room temperature. Equipment used for freezing the food products can include drum or wheel freezers having a low temperature outer surface. The food products are placed on the smooth exterior surface of the rotating drum and undergo heat exchange which causes freezing of the food products. The frozen products are then scraped off of or otherwise removed from the drum surface for packaging.
Another type of equipment frequently used in the freezing of food products is a spiral freezer that utilizes an endless conveyor belt to carry the food in a spiral path through a low temperature compartment. The conveyor belt utilized in spiral freezers typically comprises an open wire mesh which allows air to circulate through the belt to provide uniform temperature distribution around the product.
A notable problem that has developed in the freezing of many types of products is the tendency of the frozen food or other product to adhere to the belt on which it is conveyed. This problem is particularly acute in the processing of foods which contain moisture, such as chickens and other meats, because the moisture freezes to the belt. In those applications where a smooth solid belt is utilized, the frozen product can normally be removed from the belt without damaging the product. In many applications, such as in a spiral-type freezer, the belt must be of an open mesh construction to allow the cooled air to circulate through the belt to ensure uniform cooling of the product. In such applications, the moisture in the product is able to enter and freeze within the mesh openings of the belt. The frozen product can thus be difficult to remove from the belt without being damaged. If the product should be damaged, it must often be discarded or sold as a lesser grade of quality.
Another problem resulting from the use of open weave or mesh belts is the tendency of the surface of the product to conform to the surface of the belt as the product is supported thereon prior to freezing. Once the product becomes frozen, the surface markings formed in the product become solidified. While the product is not necessarily damaged by the markings formed in this manner, the visual appearance of the product may be unsatisfactory.
As a result of the damage that can result to the food or other product when mesh or otherwise perforate belts are utilized, freezers employing such belts have proven to be unsuitable for many types of food preparation processes. A need has thus arisen for an apparatus and method for reducing the incidence of food and other products freezing to the conveyor belt during the freezing process.